<template>
  <div class="music-list">
    <div class="back" @click="goBack">
      <i class="icon-back"></i>
    </div>
    <h1 class="title">{{ title }}</h1>
    <div class="bg-image" :style="bgImageStyle" ref="bgImage">
      <div class="play-btn-wrapper" :style="playBtnStyle">
        <div v-show="songs.length > 0" class="play-btn" @click="random">
          <i class="icon-play"></i>
          <span class="text">随机播放全部</span>
        </div>
      </div>
      <div class="filter" :style="filterStyle"></div>
    </div>
    <scroll
      class="list"
      :style="scrollStyle"
      v-loading="loading"
      v-no-result="noResult"
      probe-type="3"
      @scroll="onScroll"
    >
      <div class="song-list-wrapper">
        <song-list :songs="songs" @select="selectItem" :rank="rank"></song-list>
      </div>
    </scroll>
  </div>
</template>

<script>
import Scroll from '@/components/base/scroll/scroll'
import SongList from '@/components/base/song-list/song-list'
import { mapActions, mapState } from 'vuex'
const RESERVED_HEIGHT = 40

export default {
    name: 'music-list',
    components: { Scroll, SongList },
    props: {
      songs: {
        type: Array,
        default() {
          return []
        }
      },
      rank: Boolean,
      title: String,
      pic: String,
      loading: Boolean
    },
    data() {
        return {
            imageHeight: 0,
            scrollY: 0,
            maxTranslateY: 0
        }
    },
    computed: {
        noResult() {
            return !this.loading && !this.songs.length
        },
        playBtnStyle() {
          let display = ''
          if (this.scrollY >= this.maxTranslateY) {
            display = 'none'
          }
          return {
            display
          }
        },
        bgImageStyle() {
            const scrollY = this.scrollY
            let zIndex = 0
            let paddingTop = '70%'
            let height = 0
            let translateZ = 0

            if (scrollY > this.maxTranslateY) {
                zIndex = 10
                paddingTop = 0
                height = `${RESERVED_HEIGHT}px`
                translateZ = 1
            }

            let scale = 1
            if (scrollY < 0) {
                scale = 1 + Math.abs(scrollY / this.imageHeight)
            }

            return {
                zIndex,
                paddingTop,
                height,
                backgroundImage: `url(${this.pic})`,
                transform: `scale(${scale})translateZ(${translateZ}px)`
            }
        },
        scrollStyle() {
          const bottom = this.playlist.length ? '60px' : '0'
          return {
            top: `${this.imageHeight}px`,
            bottom
          }
        },
        filterStyle() {
            let blur = 0
            const scrollY = this.scrollY
            const imageHeight = this.imageHeight
            if (scrollY > 0) {
                blur = Math.min(this.maxTranslateY / imageHeight, scrollY / imageHeight) * 20
            }
            return {
                backdropFilter: `blur(${blur}px)`
            }
        },
        ...mapState([
          'playlist'
        ])
    },
    mounted() {
        this.imageHeight = this.$refs.bgImage.clientHeight
        this.maxTranslateY = this.imageHeight - RESERVED_HEIGHT
    },
    methods: {
        goBack() {
            this.$router.back()
        },
        onScroll(pos) {
            this.scrollY = -pos.y
        },
        selectItem({ song, index }) {
          // 方式一
          // this.$store.dispatch('selectPlay', {
          //   list: this.songs,
          //   index
          // })
          // 方式二
          this.selectPlay({
            list: this.songs,
            index
          })
        },
        random() {
          this.randomPlay(this.songs)
        },
        ...mapActions(['selectPlay', 'randomPlay'])
    }
}
</script>

<style lang='scss' scoped>
.music-list {
  position: relative;
  height: 100%;
  .back {
    position: absolute;
    top: 0;
    left: 6px;
    z-index: 20;
    transform: translateZ(2px);
    .icon-back {
      display: block;
      padding: 10px;
      font-size: $font-size-large-x;
      color: $color-theme;
    }
  }
  .title {
    position: absolute;
    top: 0;
    left: 10%;
    width: 80%;
    z-index: 20;
    transform: translateZ(2px);
    @include no-wrap();
    text-align: center;
    line-height: 40px;
    font-size: $font-size-large;
    color: $color-text;
  }
  .bg-image {
    position: relative;
    width: 100%;
    transform-origin: top;
    background-size: cover;
    .play-btn-wrapper {
      position: absolute;
      bottom: 20px;
      z-index: 10;
      width: 100%;
      .play-btn {
        box-sizing: border-box;
        width: 135px;
        padding: 7px 0;
        margin: 0 auto;
        text-align: center;
        border: 1px solid $color-theme;
        color: $color-theme;
        border-radius: 100px;
        font-size: 0;
      }
      .icon-play {
        display: inline-block;
        vertical-align: middle;
        margin-right: 6px;
        font-size: $font-size-medium-x;
      }
      .text {
        display: inline-block;
        vertical-align: middle;
        font-size: $font-size-small;
      }
    }
    .filter {
      position: absolute;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background: rgba(7, 17, 27, 0.4);
    }
  }
  .list {
    position: absolute;
    bottom: 0;
    width: 100%;
    z-index: 0;
    .song-list-wrapper {
      padding: 20px 30px;
      background: $color-background;
    }
  }
}
</style>
